release: prepare AgencityLab 1.2.0

[Gilbert243]

Prepare AgencityLab 1.2.0 after the Biology domain merge.

Release metadata:

• bump package/runtime version from 1.1.3 to 1.2.0
• update CITATION.cff, README and documentation release status
• move the Biology changelog entries into the 1.2.0 release section

Packaging and CI:

• update CI/runtime version assertions to 1.2.0
• update distribution artifact naming
• require twine>=7.0 so Core Metadata 2.5 distributions produced by current Hatchling are validated correctly
• add packaging smoke coverage for the public agencitylab.biology namespace

Scientific integrity:

• no canonical equation changed
• Biology remains explicitly EXPERIMENTAL
• no physical/contextual parameter is inferred or redefined by this release preparation

Local validation:

• pytest: 673 passed
• Ruff: passed
• mypy: passed
• wheel + sdist build: passed
• twine check with Twine 7.0.0: wheel passed, sdist passed

The tag v1.2.0 must only be created after this PR is green and merged into main.